With an estimated £14 million annual income and a global first print run of five million copies for her latest book, JK Rowling is in obvious senses a lucky writer but the fourth Harry Potter brings her another piece of author's good fortune - timing.

While the newspapers report the failure of England's bid to stage the football World Cup, Harry Potter And The Goblet Of Fire begins with great excitement in the wizard homes of Britain over the staging in this country of the World Cup of Quidditch, Rowling's ingenious invented game. It's such a happy coincidence that you read on half-expecting Harry to be arrested in Leicester Square after taking too many magic potions.

In fact, though the closeness to the FIFA announcement is an accident, the book feels thematically shaped to fit the summer of Euro 2000 and the Sydney Olympics. After attending a Quidditch World Cup Final marred by incidents of hooliganism aimed at 'muggles' (the non-magical) - a detail typical of the adult satire which brings Rowling her grown-up readers - Harry's new term at his scorcery school includes an international Tri-Wizard Tournament.

Most publishers will privately tell you that huge success is often ruinous to a writer's talents: the books they write poor are usually better than the ones they write rich. But the first third of this book (which is as far as embargo restrictions have allowed my household to reach at this point) suggests that Rowling still wants to write big books as well as big cheques. This is the most elaborately structured of the books, with the writing more careful than before.

Learning from other fiction series - for example, James Bond - Rowling starts with a scene (murders in a country house) which seems to have no connection with her hero until one of the villains suddenly refers to 'Harry Potter'. This produced a cheer from the five- and seven-year-old listening to my home audio-book rendition.

As a fantasy writer, Rowling is stricter than many - her universe has fixed internal rules - and, given her earnings potential in America, it's impressive that the new book includes so much fat-boy comedy (featuring Harry's muggle cousin Dudley) and parody of sports which are essentially English.

Rowling has, for the moment, changed book-publishing. She's created a world in which novels - like new cars, grouse, beaujolais nouveau and Star Wars movies - are mass-bought on the first day of availability and in which book-reviews are phoned in at half-time like a sports report. The difficulty is that inflated expectation almost inevitably encourages disappointment and backlash. But the view so far from this household is that, though no writer could justify this hype, Rowling survives it.